The present invention relates generally to the manufacture of laminated products such as may be used for flooring, counter tops, table tops, and wall panels, and more specifically to systems and methods for manufacturing such products to include a liquid resistant film and another laminate material providing a desired balancing characteristic to the laminated product.
The ability to replicate natural materials has substantially improved over the years. For example, decorative laminates have replaced natural materials in the construction of furniture, cabinets, counter tops, flooring and other surfaces. In each of these applications, a decorative surface may be applied to a core layer or substrate, namely, plywood, particle board, chipboard, hardboard, wood waste, medium density fiberboard, high density fiberboard, inert mineral board, sheet rock, plaster board and other substances. The core layer or substrate may also be made of Alternate Substrate Materials (ASM). Such ASM may include non-wood cores or substrates, such as synthetic or non-cellulose substrate material, for example, recycled plastic substrates, ABS/PC, nylon, PVC, or the like. However, a core or substrate is not included with all laminate products.
Often, a backing layer is secured to the opposite side of the substrate to balance the movement of the decorative surface or provide other benefits. It is well known in the art that traditional high pressure laminates expand or contract with an increase or decrease in the environmental humidity. Moreover, it is also known that prolonged exposure of the flooring composite, made of laminates bound to a wood-based substrate, to liquids, for example water, such as by flooding through the sub-floor, adversely effects not only traditionally constructed laminates, but also the substrate, such as by causing swelling, peaking or blistering.
Generally the decorative surface of a laminate composite, such as a laminate flooring, is designed as shown in FIG. 1. A high pressure laminate 10 may be comprised of a thin aluminum oxide incorporated overlay sheet 11 impregnated with a protective substance, such as melamine resin, which provides color fastness, hardness, chemical resistance, and also resistance to brief exposure to water. The high pressure laminate 10 may employ a decorative sheet 12 disposed under overlay sheet 11, which may be a melamine treated sheet, and sheets 13 and 14 of kraft paper impregnated with phenolic resin disposed below the decorative sheet.
Traditionally, the backing layer is similarly designed. As shown in FIG. 1, the backing layer of a decorative high pressure laminate 10 may comprise two sheets 16 and 17 of kraft paper impregnated with phenolic resin disposed below substrate 15, and a balancing layer 18 of an overlay paper impregnated with a protective substance disposed below the kraft paper sheets 16 and 17 to balance the overlay sheet 11 of the decorative side. In flooring laminates such protective substance may be a melamine resin. Typically both the backing layer and the decorative layer are bonded to substrate 15 by using a suitable adhesive.
As those of ordinary skill in the art will appreciate, the decorative and backing layers discussed above are purely exemplary and not intended to limit the description of the present invention to the above discussed structures.
After installation, such as by gluing several pieces of laminate flooring together at the seams, the decorative laminate is subject to a different environment than the backer laminate. That is, the exposed decorative laminate experiences temperature and humidity fluctuations of the room environment. In contrast, the backer laminate, is exposed to temperature and moisture changes of the sub-floor over which the laminate flooring is applied. Moreover, prolonged exposure of the backer laminate to liquids, for example water, such as by moisture penetration through the sub-floor, adversely effects not only the backer laminate but also the substrate. The traditional flooring panels are, however, not designed or otherwise properly adapted to compensate for the difference between the environments to which the decorative and backer laminates are exposed.
One inventive solution to prevent the penetration of moisture, such as water vapor or humidity into the backer layer, is to use a layer that is liquid impermeable, such as a styrenemaleic anhydride copolymer layer, at the bottom of the backing layer to substantially prevent the penetration of moisture, such as water, in liquid form. This inventive solution is disclosed in detail in the above referenced U.S. Patent Application, entitled xe2x80x9cLAMINATExe2x80x9d.
Although the incorporation of the liquid impermeable layer into the backer of the laminate flooring in accordance with a preferred embodiment of U.S. Patent Application, entitled xe2x80x9cLAMINATExe2x80x9d provides a significant improvement in the resistance of the entire composite to standing water, the sensitivity of the decorative laminate to conditions of low humidity has been discovered to increase, as in the preferred embodiment disclosed therein the melamine balancing layer 18 in the backer laminate is replaced with a liquid impermeable layer. Thus, the movement of the melamine layer 11 of the decorative side in conditions of low humidity may cause the flooring panel to warp without resistance as the liquid impermeable layer does not inflict an equal and opposite shrinkage and thus the lateral edges of the panel point in an upward direction (positive warpage). Such positive warpage of the flooring panel is visually obtrusive and often times necessitates replacement of the entire floor. The backer laminate as described in the preferred embodiment in the above referenced U.S. Patent Application, entitled xe2x80x9cLAMINATExe2x80x9d, is comprised of the liquid impermeable layer positioned at an exterior surface of one of several phenolic resin impregnated kraft paper sheets. The melamine treated balancing sheet is not incorporated into the backer laminate described in the preferred embodiment of the above referenced U.S. Patent Application entitled xe2x80x9cLAMINATExe2x80x9d as a sufficient bond may not be achieved between the liquid impermeable layer and the melamine layer. Attempts have been made to balance and/or counteract the humidity driven movement of the decorative laminate by increasing the number and weight of the phenolic resin impregnated kraft paper sheets in the backer laminate to yield a strong backer. However, such efforts did not provide a backer strong enough to balance the movement of the decorative laminate when two or more melamine treated sheets were used in the decorative laminate to improve wear resistance.
In the preferred embodiment of the above referenced U.S. Patent Application, entitled xe2x80x9cLAMINATE EMPLOYING LIQUID RESISTANT FILM AND TWO SIDED SHEETxe2x80x9d a method of incorporating a melamine treated balancing sheet in the backer laminate is described. In the preferred embodiment of the above referenced application, a layer of phenolic resin may be inserted between the liquid impermeable layer and the melamine layer so that both the liquid impermeable layer and the melamine layer may be used in the same laminate to provide the desired liquid impermeable and balancing characteristics. However, in order to properly balance a composite having a particular characteristic material associated with the exterior of the top or decorative laminate, it may be desirable to have the balancing layer close to the bottom exterior of the backer laminate. Thus, when a laminate flooring has a melamine impregnated overlay layer as a top exterior surface of the decorative side, it may be desired to have a balancing layer of melamine close to the bottom exterior of the laminate in order to properly balance the top overlay layer. However, as in the preferred embodiment of the above referenced patent application, entitled xe2x80x9cLAMINATE EMPLOYING LIQUID RESISTANT FILM AND TWO SIDED SHEETxe2x80x9d, the balancing layer is not adjacent to the liquid impermeable layer as a layer of a third substance, such as phenolic resin, is inserted between the liquid impermeable and balancing layers since the liquid impermeable and balancing layers do not readily bond with each other.
Thus, there is a need in the art for a system and method of manufacturing laminates providing the advantages of the melamine balancing layer and also providing the advantages offered by the liquid impermeable layer.
There is a further need in the art for a system and method of manufacturing laminates such that two layers, such as a balancing layer and a liquid impermeable layer, providing desired characteristics may be placed adjacent to each other in a laminate assembly.
These and other objects, features and technical advantages are achieved by a system and method for adapting a layer having a desired characteristic to be compatible with another layer having a desired characteristic, such that both layers providing desired characteristics may be used adjacent to each other in a laminate panel. For example, a substance in a balancing layer of a laminate composite, such as melamine in a melamine resin impregnated sheet, may be adapted to provide enhanced bonding with a liquid impermeable layer, such as a styrene-maleic anhydride copolymer layer.
Accordingly in an embodiment of the present invention, a balancing sheet, such as a melamine impregnated sheet, is placed adjacent to the layer providing the liquid impermeable characteristics, such as a styrene-maleic anhydride layer. The balancing sheet preferably balances the stress caused from the movement of a protective layer in the decorative laminate and prevents positive warpage of a flooring composite, for example. The styrene-maleic anhydride layer provides another desired characteristic to the composite, such as impermeability to liquids. The melamine impregnated sheet of the preferred embodiment may be adapted to provide a desired bonding with the liquid impermeable sheet. This is specially useful as traditional melamine impregnated sheets do not provide a desired bonding with the liquid impermeable sheet.
Therefore, in this embodiment of the present invention, the melamine layer and the liquid impermeable layer are placed adjacent to each other, and thus both flatness and enhanced liquid resistance may be provided to the composite employing the backer laminate. The order of the sheets in the backer laminate is changed from the traditional laminate design such that the balancing sheet is no longer the outermost layer. However, in this embodiment, the balancing sheet may be placed close to the exterior surface of the laminate to balance a corresponding layer of the decorative side thus providing a desired balancing laminate.
In the preferred embodiment, an adhesion promoting agent, such as silane, is mixed with a substance providing the desired balancing characteristic, such as melamine resin, in a predetermined amount to provide the desired adhesive characteristic to the balancing substance. In the preferred embodiment, the amount of silane added to a melamine resin used for balancing a laminate is between 0.1 to 0.5 percent by weight of the melamine resin. A laminate material may then be treated with the melamine resin, such as by coating, saturating and/or impregnating an overlay sheet with the melamine resin, using conventional methods that are well known in the art, such as by using a Kiss coater or a reverse roll coater. The melamine treated laminate material may be placed adjacent to the liquid impermeable layer and subjected to heat and pressure to cure the resin, as is known in the art, to manufacture the desired laminate having the desired liquid resistant and balancing characteristics with the layers providing the desired characteristics adjacent to each other.
In an alternative embodiment of the present invention, a first side of a laminate material, such as a sheet of kraft paper, may be treated with the melamine resin and silane mixture. The other side of the kraft paper may be treated with melamine, a mixture of melamine and silane, or a substance providing structural characteristics to the laminate, such as phenolic resin. A system and method for manufacturing such a laminate material as well as an outline of the advantages of the double treated sheet, has been disclosed in detail in the above referenced commonly assigned U.S. Patent Application, entitled xe2x80x9cSYSTEM AND METHOD FOR TWO SIDED SHEET TREATINGxe2x80x9d. Thus, in this alternative embodiment, such a sheet of kraft paper may be placed adjacent to a layer providing another desired characteristic to the laminate, such as the liquid impermeable layer, with the melamine resin treated surface next to the liquid impermeable layer to thereby dispose the layer providing the desired balancing characteristic adjacent to the layer providing the desired liquid impermeable characteristic. Such a placement of layers positions the melamine resin impregnated sheet close to the exterior of the laminate thereby providing better balancing characteristics to the laminate to substantially prevent positive warpage of the composite.
The different embodiments of the present invention as discussed above provide advantages not available in the prior art. For example, the laminate panel so constructed provides impermeability to liquids, such as water, due to the addition of the liquid impermeable layer, preferably as the outermost layer, and balancing characteristics due to the incorporation of a layer, such as the melamine resin impregnated layer, in the backer laminate, thereby allowing the composite to remain substantially flat over a broader range of temperature and humidity conditions. Moreover in the preferred embodiment discussed above, the balancing substance may be placed close to the exterior surface of the laminate as the balancing melamine layer is separated from the exterior surface of the composite by only the liquid impermeable layer, thereby providing the desired balancing characteristics. In typical laminates, the surface to be balanced, such as the melamine impregnated overlay sheet of the decorative laminate, forms the outermost surface of the decorative laminate. Therefore, it is desirable to have the balancing layer close to the exterior of the backer laminate.
Moreover, a prior art overlay sheet impregnated with the balancing substance allows only a limited amount of the balancing substance, such as melamine, to be used, and thus is not able to resist the pull of the melamine layer of the decorative laminate, especially when more than one layer of melamine resin impregnated sheet is used in the decorative side of the laminate. On the other hand, more melamine resin per unit area of the sheet may be provided to the laminate of the alterative embodiment discussed above, as kraft paper sheet is capable of absorbing more melamine than a traditional overlay sheet used in prior art backer laminates, thereby yielding a stronger backer. Thus, in the alternative embodiment discussed above, the laminate may be saturated with a greater amount of the balancing substance, such as melamine, thereby allowing the laminate to remain flat even in cases where the decorative side uses more than one melamine resin impregnated sheet to provide a desired protective characteristic to the laminate.
Therefore, it is a technical advantage of the present invention to provide a liquid impermeable laminate for use with decorative panels, such as flooring panels.
It is another technical advantage of the present invention to provide a hydrophobic laminate with the desired balancing characteristics to prevent warping of the laminate in extreme conditions.
It is yet another technical advantage of the present invention to provide a laminate with a liquid impermeable layer and a balancing layer disposed adjacent to the liquid impermeable layer.
It is still another technical advantage of the present invention to provide a liquid impermeable flooring laminate with a wood based substrate.
It is still another technical advantage of the present invention to provide a liquid impermeable flooring laminate having a core layer or substrate composed of an Alternate Substrate Material (ASM) and having the desired balancing characteristics.
It is a further technical advantage of the present invention to provide an outermost water resistant flooring laminate with a layer providing desired balancing characteristics disposed adjacent to the outermost water resistant layer.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.